Conventional sealing systems for sealing a propeller shaft in watercraft have a bush placeable onto the shaft and connectable to the shaft such that they rotate together, which bush is enclosed by a housing fixed with respect to the bush. At least one lubricant chamber open to the bush and one air chamber open to the bush is formed in the housing. The chambers are sealed with respect to each other via a seal ring. In addition, a propeller-adjacent mechanical seal encompassing the bush is provided. Via a supply line and a discharge line a continuous air stream is guided through the air chamber and thus also through the annular chamber. The lubricant chamber is associated with a continuous grease-lubricating of the at least one seal ring. However, the grease-lubricating has the disadvantage that in the event of a grease ingress into the air chamber the air lines can be blocked, with the result that they must be regularly rinsed in an expensive manner. In addition, grease is not the optimal lubricant and coolant for the seal ring preferably comprised of an elastomer, with the result that the grease-lubricating negatively impacts its service life and in particular its loadability. Due to the continuous air stream, salts and minerals that can reach into the air chamber in the event of a water ingress, are also excreted, which can also lead to a blocking of the air lines.